Calculator Form
Use the grid below. Large screens show three columns. Smaller screens show two. Mobile shows one.
Example Data Table
Example scenario: 5 V supply, 2 A load, 2 m one-way, copper conductor, 25 °C, one run, loop factor 2.
| Wire Size | Area (mm²) | Loop Resistance (Ω) | Voltage Drop (V) | Load Voltage (V) | Drop (%) |
|---|---|---|---|---|---|
| 22 AWG | 0.3260 | 0.215703 | 0.4314 | 4.5686 | 8.63 |
| 20 AWG | 0.5190 | 0.135490 | 0.2710 | 4.7290 | 5.42 |
| 18 AWG | 0.8230 | 0.085442 | 0.1709 | 4.8291 | 3.42 |
| 16 AWG | 1.3100 | 0.053679 | 0.1074 | 4.8926 | 2.15 |
| 14 AWG | 2.0800 | 0.033807 | 0.0676 | 4.9324 | 1.35 |
Formula Used
ρT = ρ20 × [1 + α × (T − 20)]
Rm = ρT ÷ (Area × Parallel Runs)
Rloop = Rm × One-Way Length × Loop Factor
Vdrop = I × Rloop
Vload = Vsupply − Vdrop
Ploss = I² × Rloop
Copper and aluminum use different resistivity values.
Higher temperature increases resistance and voltage drop.
Thicker conductors reduce drop by lowering loop resistance.
How to Use This Calculator
- Enter the supply voltage. For most uses, keep it at 5.
- Add the expected load current in amperes.
- Enter the one-way cable length from source to load.
- Choose the conductor size and material.
- Set the conductor temperature and parallel run count.
- Use a loop factor of 2 for typical two-wire circuits.
- Set the maximum acceptable voltage drop percentage.
- Submit the form and review the result, graph, and recommendation.
Frequently Asked Questions
1. Why does voltage drop matter in 5V systems?
A small drop matters more on a 5V rail. Sensors, LEDs, controllers, and USB-powered loads can fail, dim, reset, or behave unpredictably when delivered voltage falls too low.
2. What loop factor should I use?
Use 2 for normal out-and-back wiring. Use 1 only when the return path is not another cable conductor. Custom values help with unusual routing models.
3. Why does thicker wire reduce voltage drop?
Thicker wire has more cross-sectional area. That reduces resistance per meter, lowers power loss, and keeps more voltage available at the load.
4. Why does temperature change the result?
Metal resistance rises with temperature. A warm conductor drops more voltage than the same wire at 20 °C. This matters in enclosed or high-current installations.
5. Can I use aluminum wire for 5V circuits?
You can model it here, but aluminum has higher resistivity than copper. That means greater drop for the same size and length, so thicker conductors are usually needed.
6. What is a good target drop percentage?
Many low-voltage designs aim for 2% to 5%. Sensitive digital loads often benefit from stricter limits, especially when startup current spikes are possible.
7. What does the recommended wire size mean?
It is the smallest listed standard size that meets your selected voltage-drop target under the same current, length, material, temperature, and parallel-run assumptions.
8. Does this replace electrical code checks?
No. This tool estimates voltage drop and conductor behavior. Always verify ampacity, insulation rating, connector losses, safety margins, and applicable code requirements separately.